Bladder cancer begins when cells in the bladder, a hollow organ that stores urine, grow abnormally. Most bladder cancers start in the urothelial cells lining the bladder. Metastasis is when cancer cells detach from the primary tumor and spread to other body parts.
The Journey of Metastasis
Cancer cells can spread from the bladder through several pathways. One way is through direct extension, where the cancer grows outward, invading adjacent tissues and organs. This includes spread to the surrounding fatty tissues, the pelvic wall, or nearby reproductive organs like the prostate or vagina.
Another pathway involves the lymphatic system, a network of vessels and lymph nodes. Cancer cells can break away from the bladder tumor and enter these lymphatic vessels, traveling to regional lymph nodes. These lymph nodes act as filters, and cancer cells can become trapped there, forming new tumors.
The third primary method of spread is through the bloodstream, known as hematogenous spread. Cancer cells enter small blood vessels within or near the bladder tumor. Once in the bloodstream, these cells can travel to distant parts of the body, where they exit the vessels and establish new tumors.
Key Destinations of Bladder Cancer Spread
When bladder cancer metastasizes, it frequently targets specific areas of the body. Lymph nodes are often the first site of spread, particularly those in the pelvis and abdomen. Cancer in these regional lymph nodes can cause swelling and localized pain.
Bones are a common distant destination for bladder cancer cells. The spine, pelvis, and long bones are frequently affected, and symptoms can include persistent bone pain, which may worsen at night, along with a weakening of the bones that increases the risk of fractures.
The lungs are a frequent site for bladder cancer metastasis. Symptoms include a persistent cough, shortness of breath, recurring chest infections, or coughing up blood. Fluid accumulation around the lungs, known as pleural effusion, can also occur.
The liver is another common organ for bladder cancer to spread to, especially through the bloodstream. Liver metastases may cause discomfort or pain on the right side of the abdomen, nausea, reduced appetite, and unexplained weight loss. More severe signs include jaundice (yellow skin and eyes) and a swollen abdomen from fluid buildup.
Other Potential Metastatic Sites
While less common than the primary sites, bladder cancer can also spread to other parts of the body. The peritoneum, which is the inner lining of the abdomen, can be affected by the spread of bladder cancer cells. This can lead to abdominal pain and swelling.
Though less frequent, the brain is another possible site for metastasis. When bladder cancer spreads to the brain, symptoms might include dizziness, persistent headaches, or seizures. The adrenal glands, located on top of the kidneys, are also potential targets for metastasis.
Beyond these, bladder cancer can spread to other parts of the urinary tract, such as the ureters and kidneys, or to other soft tissues. In rare instances, spread has been observed to sites including the intestines, pericardium, heart, spleen, pancreas, scrotum, vagina, or the ethmoid sinus.